// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_EMULATE_ARRAY_H
#define EIGEN_EMULATE_ARRAY_H

// The array class is only available starting with cxx11. Emulate our own here
// if needed. Beware, msvc still doesn't advertise itself as a c++11 compiler!
// Moreover, CUDA doesn't support the STL containers, so we use our own instead.
#if (__cplusplus <= 199711L && EIGEN_COMP_MSVC < 1900) || defined(EIGEN_GPUCC) || defined(EIGEN_AVOID_STL_ARRAY)

namespace Eigen {
template<typename T, size_t n>
class array
{
  public:
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE T& operator[](size_t index)
	{
		eigen_internal_assert(index < size());
		return values[index];
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE const T& operator[](size_t index) const
	{
		eigen_internal_assert(index < size());
		return values[index];
	}

	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE T& at(size_t index)
	{
		eigen_assert(index < size());
		return values[index];
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE const T& at(size_t index) const
	{
		eigen_assert(index < size());
		return values[index];
	}

	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE T& front() { return values[0]; }
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE const T& front() const { return values[0]; }

	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE T& back() { return values[n - 1]; }
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE const T& back() const { return values[n - 1]; }

	EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE static std::size_t size() { return n; }

	T values[n];

	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array() {}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(const T& v)
	{
		EIGEN_STATIC_ASSERT(n == 1, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(const T& v1, const T& v2)
	{
		EIGEN_STATIC_ASSERT(n == 2, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v1;
		values[1] = v2;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3)
	{
		EIGEN_STATIC_ASSERT(n == 3, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v1;
		values[1] = v2;
		values[2] = v3;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4)
	{
		EIGEN_STATIC_ASSERT(n == 4, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v1;
		values[1] = v2;
		values[2] = v3;
		values[3] = v4;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5)
	{
		EIGEN_STATIC_ASSERT(n == 5, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v1;
		values[1] = v2;
		values[2] = v3;
		values[3] = v4;
		values[4] = v5;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5, const T& v6)
	{
		EIGEN_STATIC_ASSERT(n == 6, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v1;
		values[1] = v2;
		values[2] = v3;
		values[3] = v4;
		values[4] = v5;
		values[5] = v6;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5, const T& v6, const T& v7)
	{
		EIGEN_STATIC_ASSERT(n == 7, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v1;
		values[1] = v2;
		values[2] = v3;
		values[3] = v4;
		values[4] = v5;
		values[5] = v6;
		values[6] = v7;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE
	array(const T& v1, const T& v2, const T& v3, const T& v4, const T& v5, const T& v6, const T& v7, const T& v8)
	{
		EIGEN_STATIC_ASSERT(n == 8, YOU_MADE_A_PROGRAMMING_MISTAKE)
		values[0] = v1;
		values[1] = v2;
		values[2] = v3;
		values[3] = v4;
		values[4] = v5;
		values[5] = v6;
		values[6] = v7;
		values[7] = v8;
	}

#if EIGEN_HAS_VARIADIC_TEMPLATES
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array(std::initializer_list<T> l)
	{
		eigen_assert(l.size() == n);
		internal::smart_copy(l.begin(), l.end(), values);
	}
#endif
};

// Specialize array for zero size
template<typename T>
class array<T, 0>
{
  public:
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE T& operator[](size_t)
	{
		eigen_assert(false && "Can't index a zero size array");
		return dummy;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE const T& operator[](size_t) const
	{
		eigen_assert(false && "Can't index a zero size array");
		return dummy;
	}

	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE T& front()
	{
		eigen_assert(false && "Can't index a zero size array");
		return dummy;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE const T& front() const
	{
		eigen_assert(false && "Can't index a zero size array");
		return dummy;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE T& back()
	{
		eigen_assert(false && "Can't index a zero size array");
		return dummy;
	}
	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE const T& back() const
	{
		eigen_assert(false && "Can't index a zero size array");
		return dummy;
	}

	static EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE std::size_t size() { return 0; }

	EIGEN_DEVICE_FUNC
	EIGEN_STRONG_INLINE array()
		: dummy()
	{
	}

#if EIGEN_HAS_VARIADIC_TEMPLATES
	EIGEN_DEVICE_FUNC array(std::initializer_list<T> l)
		: dummy()
	{
		EIGEN_UNUSED_VARIABLE(l);
		eigen_assert(l.size() == 0);
	}
#endif

  private:
	T dummy;
};

// Comparison operator
// Todo: implement !=, <, <=, >,  and >=
template<class T, std::size_t N>
EIGEN_DEVICE_FUNC bool
operator==(const array<T, N>& lhs, const array<T, N>& rhs)
{
	for (std::size_t i = 0; i < N; ++i) {
		if (lhs[i] != rhs[i]) {
			return false;
		}
	}
	return true;
}

namespace internal {
template<std::size_t I_, class T, std::size_t N>
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T&
array_get(array<T, N>& a)
{
	return a[I_];
}
template<std::size_t I_, class T, std::size_t N>
EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const T&
array_get(const array<T, N>& a)
{
	return a[I_];
}

template<class T, std::size_t N>
struct array_size<array<T, N>>
{
	enum
	{
		value = N
	};
};
template<class T, std::size_t N>
struct array_size<array<T, N>&>
{
	enum
	{
		value = N
	};
};
template<class T, std::size_t N>
struct array_size<const array<T, N>>
{
	enum
	{
		value = N
	};
};
template<class T, std::size_t N>
struct array_size<const array<T, N>&>
{
	enum
	{
		value = N
	};
};

} // end namespace internal
} // end namespace Eigen

#else

// The compiler supports c++11, and we're not targeting cuda: use std::array as Eigen::array
#include <array>
namespace Eigen {

template<typename T, std::size_t N>
using array = std::array<T, N>;

namespace internal {
/* std::get is only constexpr in C++14, not yet in C++11
 *     - libstdc++ from version 4.7 onwards has it nevertheless,
 *                                          so use that
 *     - libstdc++ older versions: use _M_instance directly
 *     - libc++ all versions so far: use __elems_ directly
 *     - all other libs: use std::get to be portable, but
 *                       this may not be constexpr
 */
#if defined(__GLIBCXX__) && __GLIBCXX__ < 20120322
#define STD_GET_ARR_HACK a._M_instance[I_]
#elif defined(_LIBCPP_VERSION)
#define STD_GET_ARR_HACK a.__elems_[I_]
#else
#define STD_GET_ARR_HACK std::template get<I_, T, N>(a)
#endif

template<std::size_t I_, class T, std::size_t N>
constexpr inline T&
array_get(std::array<T, N>& a)
{
	return (T&)STD_GET_ARR_HACK;
}
template<std::size_t I_, class T, std::size_t N>
constexpr inline T&&
array_get(std::array<T, N>&& a)
{
	return (T &&) STD_GET_ARR_HACK;
}
template<std::size_t I_, class T, std::size_t N>
constexpr inline T const&
array_get(std::array<T, N> const& a)
{
	return (T const&)STD_GET_ARR_HACK;
}

#undef STD_GET_ARR_HACK

} // end namespace internal
} // end namespace Eigen

#endif

#endif // EIGEN_EMULATE_ARRAY_H
